TUZLA, Bosnia-Herzegovina (AP) _ With foreigners moving against war crimes fugitives, Bosnian Serbs have lashed out with whatever's at hand. One U.S. soldier was stabbed from behind with a sickle on Wednesday, and a grenade exploded near the house of a U.N. employee _ the third such blast this week.

The stabbing occurred less than a week after NATO troops made their first raid to seize Serb war crimes suspects. It was the first assault to wound or target a member of the NATO-led peace force since last week's raid on war crimes suspects in northern Bosnia.

The tougher Western approach has stirred Serb anger, particularly with Americans. Bombs have destroyed vehicles and damaged buildings housing international officials. Leaflets have threatened Americans and others.

Early Wednesday, a hand grenade exploded near the house of a U.N. employee in Prijedor, the third blast this week targeting international officials.

Few details were released of the attack on the U.S. soldier at a lonely outpost in Serb territory. Western officials and local Serbs said the attacker may have been nothing more than a foiled thief. U.S. soldiers said they felt comfortable with security.

``I feel more secure here than at home,'' said Staff Sgt. Mark L. Geiger, 32, of Pittsburgh, ``because here I have 8,500 soldiers who are ready to help at any time.''

Others said they thought Bosnia's chaotic traffic _ which claimed one American soldier's life this week _ was more of a danger than politically motivated violence. There are no evident increases in security.

Momcilo Krajisnik, the Serb member of the joint three-man Bosnian presidency, appealed for calm and told residents that implementing the Dayton peace agreement is in their interest.

``I want to believe that those were individual incidents,'' he said. ``It would not be good if they were some kind of revenge. They are more an expression of fear and uncertainty because of the existence of secret lists, which raise tensions and cause alarm among the people.''

Serbs have regularly criticized the existence of secret war crimes indictments, which they claim could make anyone who carried a gun in the Bosnian war a potential target for a NATO operation. International officials dismiss that as an exaggeration.

However, the attack highlighted just how isolated some of the peacekeeping troops are _ potential targets for angry Serbs.

The U.S. soldier, who was not identified, was part of a liaison team between the peace force and Serb officials in Vlasenica, 35 miles northeast of Sarajevo.

The team is based in a house. Local Serbs said they thought the attack occurred around 3 a.m., when the soldier went out to check on a commotion.

U.S. Army spokesmen in Tuzla said he was stabbed from behind with a sickle, and received treatment for a 2-inch to 3-inch shoulder wound before being released. The attacker escaped.

Peacekeeping troops and international officials are spread throughout Bosnia, often in potentially hostile territory, or on vacant stretches of road. The troops began their mission in December 1995, after a peace accord split Bosnia between a Serb substate and a Muslim-Croat federation.

Worried about troops' safety, President Clinton warned Bosnian Serbs on Tuesday that ``it would be a grave mistake'' to avenge NATO arrests of war crimes suspects.

Serbs argue they have been unfairly singled out by NATO and the international war crimes tribunal. Among secret indictments the tribunal has issued were two for Serbs Simo Drljaca and Milan Kovacevic.

Drljaca was killed by British troops when he resisted arrest near Prijedor, and Kovacevic was arrested without incident last Thursday. Both were charged with complicity in genocide for helping to organize and run detention camps for non-Serbs in the region.

Serb anger grew with the tribunal's sentencing Monday of Dusan Tadic, another Serb from the Prijedor region, to 20 years in prison.

The Bosnian government and Carlos Westendorp, the top foreign civilian official for enforcing peace, have urged NATO to keep chasing war crimes suspects, especially the Bosnian Serbs' wartime leader, Radovan Karadzic.

Serb retaliation is a small price to pay for the peace gained by capturing Karadzic, said Sarajevo government spokesman Mirza Hajric.

``We will keep on saying: do it, and do it again,'' Hajric said. ``It is a very simple question: either Karadzic, or the peace accord.''

France on Wednesday issued a firm denial of a report that it was reluctant to pursue a NATO hunt for Bosnian Serbs charged with war crimes.

The denial came in response to a New York Times article that quoted U.S. officials as saying France balked at a second raid to arrest suspected war criminals because it was too risky.

In Washington, U.S. officials also denied the report.